The present invention relates to millimeter wave power generators, and has particular relation to such generators which produce millimeter waves of high power, high coherence, high stability of frequency and phase, and high flexibility of frequency and phase.
The millimeter wave spectral region is where microwave and optical radiation merge. The conventional method of producing millimeter wave radiation is to increase the frequency of microwave radiation rather than to reduce the frequency of optical radiation. This approach is limited by the Manley-Rowe relation: the efficiency of the generator will not exceed the ratio of the frequency change. Increasing the frequency of microwave radiation by three orders of magnitude, a fairly conventional approach, therefore results in a maximum possible efficiency of 1/10th of 1%, which is undesirably low in many situations.
Reducing the frequency of optical radiation does not run into the Manley-Rowe limitation, but runs into a separate limitation of its own: lasers (a very suitable source of optical radiation) are generally low power devices themselves. Even with good efficiency, the optical power base is so low that significant millimeter wave power is, again, difficult to achieve.